Bovine respiratory disease (BRD) is the most economically costly and one of the most significant welfare problems in beef feedlot systems, affecting millions of cattle annually.
BRD causes acute respiratory distress, fever, and pain that significantly impairs welfare in affected cattle. The disease develops in the high-stress period following transport, processing, and mixing with unfamiliar cattle from multiple sources. Cattle with BRD show reduced feeding, lethargy, elevated respiratory rate, and nasal discharge. Without treatment, severe cases progress to lung consolidation and death. The reliance on antibiotics for both prevention and treatment reflects an underlying welfare and management problem that higher-welfare systems address through reduced commingling stress and improved vaccination programs.